Specific receptor-mediated inhibition by synthetic atrial natriuretic factor of hormone-stimulated steroidogenesis in cultured bovine adrenal cells

The effect of synthetic atrial natriuretic factor (ANF) on adrenal steroidogenesis has been studied in primary culture of bovine adrenal cells. ANF-(8-33) produced a potent 40-70% inhibition of angiotensin II-, ACTH-, PGE1-, and forskolin-stimulated secretion of aldosterone production from zona glomerulosa cells with an ED50 of 120 pM. An equipotent inhibitory effect of the natriuretic factor on cortisol production was also observed in cultured zona fasciculata cells. Nicotine-stimulated secretion of catecholamines from medullary cells was only slightly inhibited by the factor at doses above 10 nM. [125I]iodo-ANF-(8-33) binding to glomerulosa membranes displayed an apparent affinity of 100-150 pM for specific receptor sites and was not inhibited by angiotensin II or ACTH. Conversely, the natriuretic factor had no affinity for angiotensin II receptor sites. The results demonstrate that part of the natriuretic effect of this new factor might be due to inhibition of adrenal steroidogenesis by action through a distinct receptor.

Spontaneous [3H]noradrenaline release from the main pulmonary artery of the rabbit induced by sodium-pump inhibition

Inhibition of Na pump either by ouabain (10(-4) M) or by K removal increased the [3H]noradrenaline [( 3H]NA) release from the isolated main pulmonary artery of the rabbit in the presence of neuronal (cocaine, 3 X 10(-5) M) and extraneuronal (corticosterone, 5 X 10(-5) M) uptake blockers. The ouabain-evoked [3H]NA release began after a delay of about 30 min and peaked after 66 min of ouabain application. Both times were shortened by omission of K from the external medium. About 90% of ouabain-evoked [3H]NA release proved to be external Ca concentration ([Ca]o) dependent and the peak effect was delayed by about 80 min in Ca-free (+ 1 mM EGTA) solution. In the presence of external Ca (2.5 mM) the [3H]NA-releasing effect of 'K-free' treatment was much less pronounced than that of 10(-4) M ouabain, the initial delay in transmitter release was shorter (10-15 min) and the peak effect developed earlier (at 42 min). On readmission of K the [3H]NA release recovered quickly to the original value. Ca removal did not antagonize the transmitter release observed in K-free solution, but the peak release was delayed by about 90 min. A low concentration of ouabain (10(-5) M) failed to produce transmitter release in the presence of normal external K, but markedly increased the release in K-free solution. The release was much bigger than the sum of their separate effects, and the rate of rise was faster than when 10(-4) M ouabain was applied in normal solution. Excess Ca (7.5; 15 mM) inhibited the [3H]NA release observed in K-free solution. 7.5 mM-Ca also delayed the transmitter-releasing action of 10(-4) M ouabain, an effect antagonized by omission of K from the external medium. The mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP, 10(-5) M) significantly increased the [3H]NA release in Ca-free, 1 mM EGTA-containing solution, and enhanced the effects of ouabain (10(-4) M). The Ca ionophore A23187 (10(-5) M) also significantly increased the [3H]NA release in the absence of external Ca and in the presence of 1 mM EGTA. Again, in the presence of A23187 the effects of 10(-4) M ouabain in releasing neurotransmitter were enhanced. When CCCP and A23187 were applied together in Ca-free, EGTA solution the [3H]NA releasing action of ouabain was still apparent. Veratridine (10(-4) M) enhanced the transmitter release in the absence of external Ca in a tetrodotoxin (TTX)-sensitive manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Liquid chromatographic determination of flavor enhancers and chloride in food

A liquid chromatographic method is described for the simultaneous determination of flavor enhancers (glutamate, inosine-5'-monophosphate, and guanosine-5'-monophosphate) and chloride (salt) added to food. This rapid method exhibits excellent recoveries, and does not require derivatization or gradient elution by refractive index and UV detection in series.

Nucleotide sequence of the repressor gene of the TN10 tetracycline resistance determinant

The Tn10 tetR gene encodes the repressor that regulates transcription of the Tn10 tetracycline resistance determinant. We have determined the DNA sequence of the tetR gene and a 905 base pair region immediately 3' to tetR. The tetR gene is located on a 701 base pair HincII restriction fragment. Deletions at either end of this region eliminate synthesis of the wild-type TetR protein in E. coli minicells, and eliminate TetR activity as measured by repression of beta-galactosidase synthesis in tetA-lacZ operon fusion strains. Taken together, the DNA sequence and the genetic data indicate that tetR encodes a 207 amino acid protein with a calculated molecular weight of 23,328. This value is in good agreement with estimates of 23,000-25,000 based on electrophoretic mobility in SDS-polyacrylamide gels. There is 47% amino acid sequence homology between the deduced sequences of the Tn10 and RP1/Tn1721 TetR proteins. There is, in addition, significant amino acid sequence homology between an NH2-terminal region of the Tn10 TetR repressor and the DNA recognition regions of other DNA-binding proteins.

[3H]noradrenaline release evoked by selegiline ((-)-deprenyl) in the isolated main pulmonary artery of the rabbit

High concentrations of selegiline[-)-deprenyl) (greater than 10(-5) M) enhanced the nerve stimulation (2 Hz)-evoked release of [3H]noradrenaline from the isolated main pulmonary artery of the rabbit. This facilitation of stimulation-evoked [3H]noradrenaline release by selegiline was reduced by exogenous (-)-noradrenaline, an agonist of presynaptic alpha 2-adrenoceptors. This inhibitory action of (-)-noradrenaline was partly antagonized by yohimbine, a selective alpha 2-adrenoceptor blocker. When the stimulation-evoked [3H]noradrenaline release had already been increased by inhibition of Na+-pump (K+-free solution), selegiline further enhanced the nerve-evoked release of labelled neurotransmitter.

The inhibitory action of PGF2 alpha on release of [3H]noradrenaline enhanced by alpha 2-adrenoceptor blockade, sodium-pump inhibition and 4-aminopyridine in the main pulmonary artery of the rabbit

Large concentrations of prostaglandin PGF2 alpha inhibited the stimulation (2 Hz) evoked release of [3H]noradrenaline from the isolated main pulmonary artery of the rabbit (the inhibition caused by 3 X 10(-5) M PGF2 alpha was 62%). Furthermore, PGF2 alpha inhibited the release evoked by stimulation when it was enhanced by different procedures. During blockade of presynaptic alpha 2-adrenoceptors by 3 X 10(-7) M yohimbine, which by itself enhanced the overflow of [3H]NA in response to stimulation, the inhibitory action of PGF2 alpha was more pronounced (78.2%). In tissue in which the Na+-pump was inhibited (K+-free treatment) where the overflow of 3H was markedly increased, PGF2 alpha exerted nearly equal inhibition of transmitter release to that observed in control experiments (64.3%). The inhibitory effect of PGF2 alpha on the stimulation-evoked release of [3H]NA was less pronounced (32.1%) in the presence of 10(-4) M 4-aminopyridine (a blocker of K+-channels).

Sequence homology between the tetracycline-resistance determinants of Tn10 and pBR322

The Tn10 tetracycline resistance gene, tetA, encodes a tetracycline-inducible protein with an apparent Mr of 36 X 10(3). We have determined the nucleotide sequence of the Tn10 tetA gene. The extent of the tetA gene was determined by analysis of amino-terminal and carboxy-terminal deletion mutants. We conclude that a single Tn10 gene, the tetA gene, is sufficient to confer tetracycline resistance. The predicted Mr of the tetA protein is 43.2 X 10(3). The sequence homology between the Tn10 tetA gene and the pBR322 tetracycline resistance determinant (49% nucleotide homology, 44% amino acid homology) indicates that these phenotypically distinct tetracycline-resistance determinants must have evolved from a common ancestral sequence. The markedly hydrophobic character of the predicted amino acid sequences of the Tn10 tetA and pBR322 tet-coded proteins suggests that a substantial portion of these proteins may be embedded within the cytoplasmic membrane.

Multicopy Tn10 tet plasmids confer sensitivity to induction of tet gene expression

We inserted the Tn10 tetracycline resistance determinant (tet) into the multicopy plasmid pACYC177, and we examined the phenotype of Escherichia coli K-12 strains harboring these plasmids. In agreement with others, we find that Tn10 tet exhibits a negative gene dosage effect. Strains carrying multicopy Tn10 tet plasmids are 4- to 12-fold less resistant to tetracycline than are strains with a single copy of Tn10 in the bacterial chromosome. In addition, we find that multicopy tet strains are 30- to 100-fold less resistant to the tetracycline derivative 5a,6-anhydrotetracycline than are single-copy tet strains. Multicopy tet strains are, in fact, 10- to 25-fold more sensitive to anhydrotetracycline than are strains that lack tet altogether. The hypersensitivity of multi-copy strains to anhydrotetracycline is correlated with the effectiveness of anhydrotetracycline as an inducer of tet gene expression, rather than its effectiveness as an inhibitor of protein synthesis. Anhydrotetracycline is 50- to 100-fold more effective than tetracycline as an inducer of tetracycline resistance and as an inducer of beta-galactosidase in strains that harbor tet-lac gene fusions. In contrast, anhydrotetracycline appears to be two- to fourfold less effective than tetracycline as an inhibitor of protein synthesis. Both anhydrotetracycline and tetracycline induce synthesis of tet polypeptides in minicells harboring multicopy tet plasmids. Differences between E. coli K-12 backgrounds influence the tetracycline and anhydrotetracycline sensitivity of multicopy strains; ZnCl2 enhances the tetracycline and anhydrotetracycline sensitivity of these strains two- to threefold. We propose that the overexpression of one or more Tn10 tet gene products inhibits the growth of multicopy tet strains and accounts for their relative sensitivity to inducers of tet gene expression.

New model of a scaling dermatosis: induction of hyperproliferation in hairless mice with eicosa-5,8,11-trienoic acid

The present studies have demonstrated that topical application of a low concentration of eicosa-5,8,11-trienoic acid (a 20:3,n9 fatty acid previously reported to inhibit competitively the activity of the sheep vesicular cyclooxygenase) to skin of normal fed hairless mice produced severe scaly dermatosis which is characterized by marked hyperplasia and acanthosis of the epidermal layer. The precise mechanism of this induction of scaly dermatosis is presently unclear. It is nonetheless interesting that the treatment of skin with similar concentrations of other unsaturated fatty acids produced no visible or histologic effects. Furthermore, endogenous levels of arachidonic acid in epidermal phospholipid and triglyceride fractions were shown to increase significantly (p < 0.01) in skin treated with the 20:3,n9 fatty acid while the endogenous level of PGE2 in the same tissue decreased markedly. This latter observation is consistent at least in part, with a previous report from this laboratory in which the 20:3,n9 fatty acid inhibited in vitro the activity of the sheep vesicular cyclooxygenase (the rate limiting enzyme in the transformation of arachidonic acid into the prostaglandin endoperoxides) although the increase in arachidonic acid may also reflect an increased incorporation of this fatty acid into the epidermal lipids by the hyperproliferative tissue. Evaluation of the proliferative status of 20:3,n9 fatty acid-treated skin showed a significant increase (p < 0.01) in labeling and mitotic indices. The use of this potentially endogenous fatty acid may be a useful tool for further investigations of hyperproliferative skin diseases where dietary deficiency of essential fatty acids does not exist.

[Ischemic hepatitis. Clinico-pathological presentation of 2 cases]

Just before death, two female patients with congestive heart failure exhibited marked elevation of cytolytic hepatic enzymes, suggesting the diagnosis of viral hepatitis. Histologic examination of autopsy material led us to conclude in both cases on the presence of extensive and confluent ischemic centrizonal necrosis (shock liver). This picture probably reflected the consequences of liver perfusion failure. Ischemic hepatitis is the association of shock liver with marked elevation of transaminases.

Field-flow fractionation of alkali-liberated nuclear polyhedrosis virus from gypsy moth Lymantria dispar Linnaeus

Rod-shaped viral particles of the gypsy moth nuclear polyhedrosis virus (NPV) were obtained through alkaline dissolution of inclusion bodies isolated and purified from infected hosts. The liberated viral fraction contains a wide assortment of enveloped aggregated forms as well as enveloped monomers. This complex mixture was separated by means of sedimentation field-flow fractionation (sedimentation FFF) to give a mass spectrum of the separated particles. From the elution pattern effective molecular weights could be assigned to the various resolved components. Through electron microscopy it was possible to characterize the components as monomers, dimers, etc. In parallel experiments the same viral mixture was separated by the more commonly used density gradient sedimentation technique. The two methods are compared as to time and convenience of manipulation, as well as to the amount of physicochemical information that can be extracted from each separation. The mixture of aggregate viral structures was dialyzed against a nonionic detergent solution. Sedimentation FFF of the dialysate revealed a uniform population of non-enveloped particles with no effective molecular weight which was lower than that of the initial monomer fraction. Electron microscopic observations confirmed that this lower molecular weight fraction did indeed contain rod-like structures which were thinner than the initial enveloped monomers indicating that most if not all of the enveloped material had been removed from the viral rod structures.

Hepatic delta 9 and delta 6 desaturase activities during the recovery period following carbon tetrachloride poisoning

The liver microsomal delta 9 and delta 6 desaturase activities have been studied in rats with carbon tetrachloride-induced hepatitis. Immediately after poisoning, significant decreases were observed for both types of desaturase activity. However, recovery kinetics were slower for the delta 6 desaturase than for the delta 9 desaturase. The activities of NADH-ferricyanide and NADH-cytochrome C reductases, proteins involved in the electron transfers associated with microsomal desaturation, were also measured. There was a fall in both activities after poisoning, but this decrease was less than that of the desaturase activities.

Effect of renal microsomes and renal lysosomes on in vitro hepatic fatty acid synthesis

An inhibitor and stimulator of in vitro hepatic fatty acid synthesis are present in renal microsomes. In addition, a stimulator of fatty acid synthesis is present in renal lysosomes. Renal microsomal inhibition of hepatic fatty acid synthesis is not due to the depletion of cofactors in the system. This inhibitor appears to be located exclusively in the kidney medullary microsomes. It is destroyed by Pronase and heat treatment suggesting it may be a protein. Its effects on fatty acid synthesis may be attributed in part to ATPase activity as well as a direct effect on the hepatic fatty acid synthesizing system. A stimulator of hepatic fatty acid synthesis is present in the buffer insoluble fraction of an acetone powder preparation of renal microsomes. This stimulator is relatively heat labile and does not appear to be a phospholipid. The lysosomal stimulator of hepatic fatty acid synthesis is associated with the contents of renal lysosomes and not with the lysosomal membranes. It acts at the acetyl-CoA carboxylase step and its activity is not affected by fasting or aminonucleoside induced nephrosis.